Gripping device



May ,1946 E. B. COOPER m1. 2,401,050

GRIP-PING DEVICE Filed Feb. 21, 1944 atenied ay 2%, 6

sitin PING DEVHCE Application February 21, 1944, Serial No. 523,216

loose in the links when the ammunition belts are subjected to conditionsof high humidity and, further, repeated torsional stress of theammunition belts under tensional loads likewise tends to work thecartridges loose, this being known as "walking out of the cartridges.

An object of the present invention is to provide an improved grippingdevice, particularly a link for ammunition belts. A further object is toprovide a plastic link for ammunition belts which will hold cartridgessecurely regardless of atmospheric conditions or any ordinary stressesto which the ammunition belt may be subjected in use. Other objects willbe apparent frcm'the description of the invention given hereinafter.

, The above objects are accomplished according to the present inventionby providing a link for ammunition belts which link is formed of aplastic of high rigidity, form stability, and toughness, and comprises abody member, a pair of annular cartridge receiving ringsin axial align-'ment, spaced from each other and rigidly interconnected by the bodymember, an ofiset annular ring rigidly connected to the body memberbetween the pair of cartridge receiving rings and providing theconnecting means to a similar succeeding link, each of the cartridgereceiving rings having a plurality of longitudinal cantilever membersfor engaging an inserted cartridge and each of the cantilever membersextending slightly inwardly to a point whose distance from the center ofthe ring is less than the radius of the tridge to be inserted.

In a preferred embodiment of the invention, each cantilever member ofeach of the pair of cartridge receiving rings extends inwardly to apoint whose distance from the center of thering is less than the radiusof the cartridge to be inserted, to at least such extent that the freeend of the cantilever member, when in cartridge gripping position, isdisplaced from its idle position a distance which is a substantialmultiple of the cardistance its point of support may be displaced fromthe center of the ring by the expansive efiect of water absorption onthe ring. Further, the ofiset annular ring is preferably slotted as willbe described hereinafter.

While the link of the present invention when made of any suitableplastic, is designed to overcome dimculties encountered with linksheretofore available, the selection of the plastic is, nevertheless,important in providing a link best adapted for use in ammunition belts.It is preferred that the link should be made of a plastic having thefollowing properties:

Rigidity.The modulus of elasticity in tension, as determined by ASTMmethod D638-42T, should be at least 300,000 lbs. per square inch;

Form stability.--A test piece of the plastic subjected at 100 F.- in airsaturated with moisture, to a continuous fiexural load which develops inthe piece a maximum fiber stress of 1,000 lbs. per square inch, shouldsufier therefrom no more than negligible permanent deformation;

Toughness-The hand-break number, determined as described in ModernPlastics, volume 21, No. 3, page 118 (November 1943) should be at least90.

Among the plastics meeting the above requirements are certain syntheticlinear polymers; some of which do not require any modification andothers of which need to be compounded with appropriate auxiliaryingredients. A preferred member of this group is the synthetic linearpolymer polyhexamethylene adipamide which meets the above statedrequirements when its intrinsic viscosity (as defined in Carothers U. S.Patent 2,137,235) is greater than 1.0.

Regardless of the specific plastic selected for use in'the presentinvention, it should be a plastic characterized by high rigidity, formstability, and toughness, even though it may not fully meet the abovestated requirements. The invention will be more specifically describedwith reference to the accompanying drawing wherein: v

Fig, 1 is a side elevation of a fragment of an ammunition belt in whichare shown in operative position two 1inks embodying a preferred formFig. is an end elevation of the same link, looking in the direction ofthe arrows H in Fig. 2.

The'cartridge link of this invention is prefercantilever member 0 is asubstantial multiple of the distance its point bf support is displacedfrom the center of the ring, the decrease in gripping strength will benegligible. The effects of temperature variations are similar to thoseof moisture absorption but of lesser imp r n If t reverse phenomenonoccurs, ,e. g., shrinking of the rings, the cantilever member 0 will bedis- A fragment of an assembled ammunition belt is shown in Fig; l. Thecartridge 5 passes through the receiving rings 2 and 3 of one link andthe offset ring 4 of the succeeding link and, hence, functions as apintle to secure adjacent links of the belt to each other. As eachcartridge of the ammunition belt reaches the machine gun mechanism, itis automatically withdrawn from the link carrying it and, of course, thelink falls free and the ammunition belt disintegrates.

A feature of this invention resides in the construction of the cartridgereceiving rings 2 and 3. Ring 2 is designed to fit around the neck ofthe cartridge and ring 3 to fit around the body of the cartridge, asshown clearly in Fig. 2. For convenient identification, they will bereferred to as neck ring 2 and body ring 3, respectively. Both ringscomprise a plurality of longitudinal canti- 1 torsional stresses.

placed slightly more but the net overall magnitude of gripping actionwill be only negligibly increased and the grip will not be obiectionablytight. I

It has been found that the application of repeated torsional stress toan ammunition belt held under tensional load tends to work thecartridges loose from their links as the result of force exerted byone'link on the next one through the offset ring 4 which functions asthe coupling I between the two links. This offset ring 4 normally fitsloosely on the cartridge but has a tendency to bind when undercombinedtensile and ring 4 binds on the cartridge, it pushes against the neckring 2 of the succeeding link and forces that link slightly down theneck of the cartridge inserted therein with the result that thecartridge will work loose or walk out and possibly lever members 8adapted to grip the cartridge to be inserted. As shown more clearly inFigs.

2 and 3, each of these cantilever members 8 of each of the rings 2 and 3extends slightly inwardly and it must reach a point whose distance fromthe center of the ring is less than the radius of the cartridge ,to beinserted so that, in cooperation with-the other members 6 of the ring,it will grip and hold the cartridge securely. When a cartridge isinserted into a pair of these rings and pushed into gripping position, aconsiderable frictional resistance develops at the extremities of thecantilever members 6 which have been forcibly spread apart because ofthe diameter of the cartridge exceeding the inside diameter of theextremities of the cantilever members 6.

It is preferred to design the link according to this invention so that,when the cartridge has been inserted far enough to insure an adequategrip, the interior taper of the neck ring 2 matches that of the shoulderof the cartridge 5, as shown in Fig. 2, so that the distance eachcartridge is inserted in its link will be controlled and a uniformammunition belt will be obtained.

After the cartridge 5 has been inserted into rings 2 and 3, thedeformation of the extrema ties of the cantilever members 6 ispreferably such that each is displaced from its idle position by anamount much greater than the amount to which its supported end can bedisplaced by expansion of the ring resulting from water absorption bythe plastic material of which the ring is made. As an illustration, alink made in accordance with the present invention, when placed over acartridge, has the extremities of its cantilever members 6 displacedradially by about 0.040 inch. If the link is now placed in a highlyhumid atmosphere causing an expansion of the rings to yieldan elongationof the periphery of each ring by about 0.19 inch, there results a radiusexpansion of about 0.0022 inch. ,This expansion will have no practicaleffect upon the flexural stresses inasmuch as 0.0022 inch is many timesless than 0.040 inch. Since the deflection of achv prevent operation ofthe machine gun.

This diillculty with the cartridge working out of the link has beenovercome according to the present invention by providing the offset ring4 -with a slot 1 through its walls transverse to its axis and extendingaround its circumference to adjacent the portion adjoining the bodymember I.

The provision of the slot 1 results in a bindin of the cartridge on oneside of the oflset ring 4 while the other, side of the offset ring 4pushes against the next link. Therefore, instead of forcing the link offthe cartridge, the force causes the slot 1 to partially close, theeffort being ex-' pended in deforming the ring 4 rather than in movingthe next link. In an offset ring V2 inch wide, a inch slot has beenfound satisfactory. Ordinarily, the slot I is made approximatelyequidistant from the ends of the ring. In any event, the determinationof the slot width and position is made on the basis of the forcerequired to deform the slot which force should be substantially lessthan that required to move a link I on the cartridge. I

A further feature of the present invention is found in the design of thebody ring I to facilitate the action of a pair of pawls in the machinegun mechanism which advances the ammunition belt. Dimculty heretoforeencountered with the pawls slipping on the surface of the body ring hasbeen eliminated by providing a pair of shoulders 0 (see Figs. 3 and 4)on the body ring I. A further improvement in the design of the linkeliminates buckling of the links as they pass through automatic linkloading machines. This improvement consists in the strengthening member9 made as an integral part of the body ring 3 (see Figs. 3 and 4) and asimilar strengthening member i0 and two additional strengthening membersH, II made as an integral part of the neck ring 2 (see Figs. 3 and 5).

While the invention has been described withparticular reference to thespecific embodiment shown in the drawing, it will be understood thatthis is merely illustrative and that the design of th link may be variedconsiderably without departing from the scope of the invention. Fur- Atthe same time the offset ther, the grippin device of the presentinvention is not only useful as an ammunition belt link but generallywhere belts of the type herein desecurely regardless of atmosphericconditions andthey eliminate the walking out of cartridges fromammunition belts. Further, the present links have a strength andrigidity which overcomes any tendency to buckle as the links are handledin automatic loading machinery.

As many apparently widely difierent embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that the invention is not limited to the specific embodimentsthereof except as defined in the appended claims.

We claim:

1. A link for ammunition belts in which car tridges form the pintles ofthe belt, said link bein formed of a plastic of high rigidity, formstability, and toughness, and comprising a body member, a pair ofannular cartridge receiving rings in axial alignment, spaced from eachother and rigidly interconnected by said body member, an oiiset annularring rigidly connected to said body member between said pair ofcartridge receiving rings and providing a connecting means to a similarsucceeding link, said offset rin being slotted transversely to its axisthrough its walls at a point approximately equidistant from its ends andaround its circumference to adjacent the portion thereof adjoining saidbody member, each of said cartridg receiving rings comprising aplurality of longitudinal cantilever members for engaging an insertedcartridge and each of said cantilever members extending continuouslyslightly inwardly so that its free end is positioned at a point whosedistance from the center of said ring is less than the radius of thecartridge to be inserted.

2. A link for ammunition belts in which cartridges form the .pin'tles ofthe belt, said link being formed of a plastic of high rigidity, formstability, and toughness, and comprising a body member, a pair ofannular cartridg receivingrings in axial alignment, spaced from eachother and rigidily interconnected by said body member, an offset annularring rigidly connected to said body member between said pair ofcartridge receiving rings and providing a connecting means to a similarsucceeding link, said offset ring being slotted transversely to its axisthrough its walls at a point approximately equidistant from its ends andaround its circumference to adjacent the portion thereof adjoining saidbody member, each of said cartridge receiving rings comprising aplurality of longitudinal cantilever members for engaging an insertedcartridge and each of said cantilever members extending continuouslyslightly inwardly so that its free end is positioned at a point whosedistance from the center of said ring is less than the radius of thecartridge to be inserted, to at least such extent that the free end ofsaid cantilever member, when in cartridge gripping position, isdisplaced from its idle position a distance which is a substantialmultiple of the distance its point of support may be displaced from thecenter of said ring by the expansive effect of water absorption by saidring.

3. A link for ammunition belts in which cartridges form the pintlesofthe belt, said link being formed of polyhexamethylene adipamide havingan intrinsic viscosity greater than 1.0, and said link comprising a bodymember, a pair of annular cartridge receiving rings in axial allgn ment,spaced from each other and rigidly interconnected by said body member,an offset annular ring rigidly connected to said body member betweensaid pair of cartridge receiving rings and providing a connecting meansto a similar succeeding link, said ofiset ring being'slottedtransversely to its axis through its walls at a point approximatelyequidistant from its ends and around its circumference to adjacent theportion thereof adjoining said body member, each of said cartridgereceiving rings comprising a plurality of longitudinal cantilevermembers for'engaging an inserted cartridge and each of said cantilevermembers extending continuously slightly inwardly so that its free end ispositioned at a point whose distance from the center of said ring isless than the radius of the cartridge to be inserted.

EnwARn B. COOPER. MAURICE L. MACHT.

